As a result of the rapidly growing energy needs of modern life, the development of high performance electrical energy storage devices has gained significant attention. Supercapacitors are promising electrical energy storage devices with properties intermediate between those of batteries and traditional capacitors, but are being improved more rapidly than either. Over the past couple of decades, supercapacitors have become key components of everyday products by replacing batteries and capacitors in an increasing number of applications. The future growth of this technology depends on further improvements in energy density, power density, cycle life and production cost.